A catalytic converter for a vehicle comprises in general a canned and coated catalytic converter substrate in flow communication with inlet and outlet passages. It is positioned on the exhaust side of the internal combustion engine of the vehicle in order to treat exhaust gas emissions from the engine.
During cold start and warming-up of the engine, the catalytic converter is not sufficiently heated for optimum performance and the exhaust gas emissions may therefore pass through the catalytic converter without catalytic conversion thereof. To improve the heating properties, the catalytic converter is often positioned as close as possible to the exhaust ports. To accelerate heating, it is also possible to heat the catalytic converter electrically or to temporarily control combustion such that the temperature of the exhaust gas heat flow is increased.
A frequent problem also particularly during cold start is that emissions in liquid form exit the engine. This may be caused by liquid fuel and oil which passes the engine during cranking of the engine, prior to combustion. Moreover, during cold start, exhaust gases might condense on cold walls and for liquid fuel and oil.
A solution to one or more of the abovementioned problems used by some manufacturers is a so called hydrocarbon trap. Due to the fact that the catalytic converter substrate is not warm enough for catalytic conversion and that the concentration of hydrocarbon is high during cold start, a hydrocarbon trap where a trap material is coated on a typical catalytic converter substrate may be needed. The trap material stores hydrocarbon at low temperatures and releases hydrocarbon at higher temperatures. The trap material is, however, sensitive to aging.
Moreover, catalytic converters typically need protection to avoid overheating which may otherwise occur at full load operation. Overheating can be avoided by over-fueling but that also causes the catalytic converter to operate at sub-optimal conditions, leading to an increase in tail-pipe emissions.
EP 2453113 provides an improved exhaust-gas aftertreatment device where deflector means are used to collect and retain emissions in liquid form in a cold start phase until the deflector means has been sufficiently heated for the emissions to evaporate.
However, there is still room for improvement of the above exhaust-gas aftertreatment device, in particular with respect to the life length of the catalytic converter material in high performance engines.